Critical synthesis of the electrochemical characterization of chemically modified zeolites and aluminophosphates

Zeolites that have been chemically modified by incorporating transition met al complexes in their porous network and molecular sieves chemically modifi ed by incorporating transition metal in their framework have led to numerou s applications of which the most widespread is undoubtfully catalysis. Howe ver, the catalytic activity of these inorganic compounds is still not well understood and there is a lack of evidence concerning the encapsulation eff iciency of complexes within the zeolites and the location of transition met als inside the framework of molecular sieves. Numerous studies have shown t hat zeolite encapsulation has an influence on the redox behaviour of these complexes, such as in preventing aggregation or the dimerization process. M oreover, analysis of the electrochemical process at this type of modified e lectrode demonstrates solvant and electrolyte effects on the electroactivit y of the encapsulated complexes. However, these different studies highlight ed the unsatisfactory electrochemical accessibility of intrazeolitic or fra mework species. Thus, we undertake here a discussion of the different strat egies reported in the literature aimed at promoting the electroactivity of these molecular materials.